Solution on macOS High Sierra when iShowU Audio Capture or other Kext cannot be installed - Kext rejected due to system policy
I needed to use OBS Studio to capture some video/audio from my desktop. On Mac OS X that in turn requires installing iShowU Audio Capture. That installation should be trivially easy, but it took me 2 weeks to work out how to get it installed, and a long email thread with the Shiny White Box support staff. The problem was the installation required that I give permission, but giving permission meant opening up the System Preferences to the Security pane and clicking on a button, and clicking on that button did not work. There is a fairly long list of possible suggestions that I have to share.